This invention relates generally to wear indicators for use with a brake having a brake wear adjuster and more particularly to a brake wear indicator that provides a positive feedback indicating unacceptable brake wear.
In an air brake, as is known in the prior art, an S-shaped cam at the end of a cam shaft is rotated by a slack adjuster lever to activate the brake shoes and put them in contact with the brake drum to slow or stop the vehicle. As wear occurs in the brake linings, the S-cam must be adjusted by rotation of the cam. Adjustments are made in the brake cam by rotation of the cam shaft relative to the slack adjuster lever. Adjustment beyond a certain point can result in a failure of the brake to set and can result in failure of the brakes in use. Since multiple parties may do the adjustment on the brakes, it is important that a person responsible for maintaining the brakes to readily determine the amount of brake lining wear. One way of doing this is by visual inspection of the brake lining. Because of the relative inaccessibility of the brake cam and the brake linings, it is desirable to have a visually observable wear indicator. It is even more desirable to have a wear indicator that may be tactilely observed by the maintenance person. This is particularly desirable where the brake assembly uses stone shields to exclude foreign material. Visual access to the brake lining is further reduced.
The foregoing illustrates limitations known to exist in present brake wear indicators. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
In one aspect of the present invention, this is accomplished by providing a brake wear indicator which uses a body having a pair of resilient fingers in an outer circumferential wall with a wear limit lug at the end of each finger. Positioned within the body is a rotatable brake wear disk which is connected to the brake adjuster cam. The brake wear disk has a wear detector lug thereon. As the brakes are adjusted to compensate for brake lining wear, by rotating the cam shaft relative to a slack adjuster lever, the brake wear disk rotates relative to the body. When the brakes are reaching the limit of their adjustment, the wear detector lug contacts one of the wear limit lugs. Continued rotation of the cam shaft relative to the slack adjuster lever results in the end of the finger being lifted above the outer surface of the body, thereby indicating unacceptable brake wear.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures.